High temperature fuel cell systems are known for their efficient use of fuel to develop DC and or AC electric power. Under normal operation, a typical high temperature fuel cell system, like a SOFC, system maintains a system temperature of approximately 700° C. For the high temperature fuel cell system to become operational, the system typically requires significant startup time, ranging anywhere between 1 to 4 hours from near ambient environmental conditions. When the system is not required to provide power, the typical system may be kept in a hibernation mode, whereby the normal fuel and air processes are reduced, stopped, or the system is allowed to cool. However, to avoid the significant time delay each time the high temperature fuel cell system is restarted from hibernation mode, it is desirable to maintain the internal system temperatures reasonably close to the normal system operation temperatures.
Maintaining internal temperatures of high temperature fuel cell systems during a hibernation mode allows for rapid recovery to a power producing operation mode. One known method for maintaining approximate operational level internal temperatures of the high temperature fuel cell system requires heating the high temperature fuel cell system with the system's base fuel stock through a combustor/recuperator system. Another known method for maintaining the internal temperature of the high temperature fuel cell system is to immerse the high temperature fuel cell system into a separate burner. Both methods require a significant amount of fuel and air supply flows to maintain heat and require controls that consume both significant amounts of fuel and parasitic power that waste a portion of the efficiencies achieved by the high temperature fuel cell system when in operation. Moreover, these methods create significant noise, vibration and exhaust emissions.
For the reasons stated above, and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an improved method and system for near operational level internal temperatures of a high temperature fuel cell system during a hibernation mode without an increase in manufacturing costs.